From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1993114533C; Fri, 29 Mar 2024 12:28:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711715288; cv=none; b=HCmELVMbml5zFXrB7e3qiwlBf6ftkq3giLN6rmbPNjuBUEi7sEOD7lpzfOtEH3A9rPq5QYof+YB1yeKJ86OAYk6/+PqQuzFhevOcsTf2uXoo5bPv2fwaST/8wKbtJch1QAIa6FgKUufjcKhfcEw04nU9lhpcFDuzyB6MQqRuKsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711715288; c=relaxed/simple; bh=ky+gsxc5QdHdpGdLpqgXyT53m5u9rjRLRmzsqSEwCPk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iM/cpZJSKH1As0wwixGcgKbi/YOQPCmYV2J6MCNXgEzHNbdKuf3EcuitxIi3/t26licTh+oegmbNBnUi9g16EOugE1orTWy4SffaiOzfZzPKpUQ7tX/83md2iHOVIM0huaOvw35aItaHyckfd7IueajOXQGKSuqC1BKd9CHcuVY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=op1eBtoU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="op1eBtoU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8F4CC43390; Fri, 29 Mar 2024 12:28:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711715287; bh=ky+gsxc5QdHdpGdLpqgXyT53m5u9rjRLRmzsqSEwCPk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=op1eBtoUlIbau4KgDl5zSGrdTLG4wEPAMjXdji/GJgtfNaYBuzvl4h0Z7Aac3Limk lzsYswjSi836J2dj5cOeL02ntiTPjhOx+7M9agyLuTkgcNr2teoFyQB3Yp0bTLHNZY SQS5HN6C1j6GFZun0q+4S3aAikUYc69ORBr5Ldr7XQY+qX0J+j9OB8bbWCwuyCCgJM e6McpfgU+ZYGqEb4Z82P80DGjChWd87L2toqerkXufielxdyTUmwWYzk83tWPO11Nb VGQkba91ZSkMQfHX4QFLDqt8EiPxcSD+N5ntUg+eylCDhRRNM208t1xB6YeyBa7PkO SxA9dOREXyeCg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Florian Westphal , Simon Horman , Paolo Abeni , Sasha Levin , kuba@kernel.org, davem@davemloft.net, edumazet@google.com, dhowells@redhat.com, linyunsheng@huawei.com, almasrymina@google.com Subject: [PATCH AUTOSEL 6.8 38/68] net: skbuff: add overflow debug check to pull/push helpers Date: Fri, 29 Mar 2024 08:25:34 -0400 Message-ID: <20240329122652.3082296-38-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240329122652.3082296-1-sashal@kernel.org> References: <20240329122652.3082296-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.8.2 Content-Transfer-Encoding: 8bit From: Florian Westphal [ Upstream commit 219eee9c0d16f1b754a8b85275854ab17df0850a ] syzbot managed to trigger following splat: BUG: KASAN: use-after-free in __skb_flow_dissect+0x4a3b/0x5e50 Read of size 1 at addr ffff888208a4000e by task a.out/2313 [..] __skb_flow_dissect+0x4a3b/0x5e50 __skb_get_hash+0xb4/0x400 ip_tunnel_xmit+0x77e/0x26f0 ipip_tunnel_xmit+0x298/0x410 .. Analysis shows that the skb has a valid ->head, but bogus ->data pointer. skb->data gets its bogus value via the neigh layer, which does: 1556 __skb_pull(skb, skb_network_offset(skb)); ... and the skb was already dodgy at this point: skb_network_offset(skb) returns a negative value due to an earlier overflow of skb->network_header (u16). __skb_pull thus "adjusts" skb->data by a huge offset, pointing outside skb->head area. Allow debug builds to splat when we try to pull/push more than INT_MAX bytes. After this, the syzkaller reproducer yields a more precise splat before the flow dissector attempts to read off skb->data memory: WARNING: CPU: 5 PID: 2313 at include/linux/skbuff.h:2653 neigh_connected_output+0x28e/0x400 ip_finish_output2+0xb25/0xed0 iptunnel_xmit+0x4ff/0x870 ipgre_xmit+0x78e/0xbb0 Signed-off-by: Florian Westphal Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20240216113700.23013-1-fw@strlen.de Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- include/linux/skbuff.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 2dde34c29203b..fd9198fcc3c30 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2642,6 +2642,8 @@ static inline void skb_put_u8(struct sk_buff *skb, u8 val) void *skb_push(struct sk_buff *skb, unsigned int len); static inline void *__skb_push(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + skb->data -= len; skb->len += len; return skb->data; @@ -2650,6 +2652,8 @@ static inline void *__skb_push(struct sk_buff *skb, unsigned int len) void *skb_pull(struct sk_buff *skb, unsigned int len); static inline void *__skb_pull(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + skb->len -= len; if (unlikely(skb->len < skb->data_len)) { #if defined(CONFIG_DEBUG_NET) @@ -2674,6 +2678,8 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta); static inline enum skb_drop_reason pskb_may_pull_reason(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + if (likely(len <= skb_headlen(skb))) return SKB_NOT_DROPPED_YET; -- 2.43.0